The present invention relates to a copolymer of cyclopentadiene and/or dicyclopentadiene and a vinyl-substituted aromatic compound, the hydrogenated product thereof, and a process for producing the same. More specifically, the present invention relates to a copolymer of cyclopentadiene and/or dicyclopentadiene and a vinyl-substituted aromatic compound having a sharp molecular weight distribution, namely, a low weight average molecular weight (hereinafter abbreviated as xe2x80x9cMwxe2x80x9d)/number average molecular weight (hereinafter abbreviated as xe2x80x9cMnxe2x80x9d) ratio, a hydrogenated product thereof, and a process for producing the same.
It has been known that a copolymer of cyclopentadiene and/or dicyclopentadiene (hereinafter sometimes referred to as xe2x80x9c(di)cyclopentadienexe2x80x9d) and a vinyl-substituted aromatic compound is useful as a substrate of an adhesive, a tackifier, a paint or the like.
This copolymer has been produced so far by mixing (di)cyclopentadiene with a vinyl-substituted aromatic compound in a solvent such as xylene or the like for copolymerization (Japanese Patent Publication No. 1442/1986).
The copolymer obtained by this method exhibits, however, an Mw/Mn ratio of more than 5, having a broad molecular weight distribution. Accordingly, this copolymer shows quite a high melt viscosity. When it is incorporated into, for example, an ethylene-vinyl acetate copolymer to form a hot-melt tackifier or adhesive, a workability is poor disadvantageously.
To cope with this drawback associated with the conventional method, the present Applicant proposed a process in which the heat polymerization is conducted by adding dropwise (in divided portions) a mixture of (di)cyclopentadiene and a vinyl-substituted aromatic compound to a solvent such as xylene or the like (Japanese Patent Publication No. 88412/1995).
This process can give a sharper molecular weight distribution than the method in which the heat polymerization is conducted by charging the mixture of (di)cyclopentadiene and the vinyl-substituted compound into the solvent.
The copolymer obtained by this process exhibits indeed an Mw/Mn ratio of 5 or less which is lower than the copolymer obtained by the conventional method, but this ratio is actually approximately 2.8 as will be shown in Examples, and the value is not always/necessarily satisfactory at present. When this copolymer is used as a starting material of a tackifier or an adhesive, a melt viscosity is not altogether satisfactory. Accordingly, its solution has been in demand.
The present invention aims to provide a copolymer of (di)cyclopentadiene and a vinyl-substituted aromatic compound which has a sharper molecular weight distribution and by which it is possible to solve the above-mentioned problems of the conventional method and to produce a higher-performance tackifier or adhesive, a hydrogenated product thereof, and a process for producing the same.
In order to solve the above-mentioned problems of the conventional method, the present inventors have conducted assiduous investigations. Consequently, they have found that when the copolymerization is conducted by adding a mixture of (di)cyclopentadiene and a vinyl-substituted aromatic compound to a solvent at a specific ratio based on a total amount of (di)cyclopentadiene and the vinyl-substituted aromatic compound as starting monomers in divided portions, an Mw/Mn ratio of the resulting copolymer is surprisingly reduced to 2.5 or less.
Further, the present inventors have found that when (1) a sulfur compound or (2) at least one compound selected from a group consisting of a hydroxybenzene compound, a hydroxynaphthalene compound and a quinone compound is caused to exist in adding a mixture of (di)cyclopentadiene and a vinyl-substituted aromatic compound to a solvent in divided portions, the Mw/Mn ratio of the resulting copolymer is more reduced to less than 1.9.
These findings have led to the completion of the present invention.
That is, the first invention is to provide a copolymer of cyclopentadiene and/or dicyclopentadiene and a vinyl-substituted aromatic compound, said copolymer having a softening point of from 60 to 130xc2x0 C., a vinyl-substituted aromatic compound content of from 30 to 90% by weight, a bromine number of from 30 to 90 g/100 g, a number average molecular weight of from 400 to 1,000, and a weight average molecular weight/number average molecular weight (Mw/Mn) ratio of 2.5 or less.
The second invention is to provide a process for producing the copolymer of the first invention, which comprises conducting the copolymerization while adding a mixture of cyclopentadiene and/or dicyclopentadiene and a vinyl-substituted aromatic compound to a solvent in divided portions to produce a copolymer of cyclopentadiene and/or dicyclopentadiene and the vinyl-substituted aromatic compound, wherein the solvent is used in an amount of from 50 to 500 parts by weight per 100 parts by weight in total of cyclopentadiene and/or dicyclopentadiene and the vinyl-substituted aromatic compound.
The third invention is to provide a hydrogenated product of a copolymer of cyclopentadiene and/or dicyclopentadiene and a vinyl-substituted aromatic compound which is obtained by hydrogenating the copolymer of the first invention, and which has a softening point of from 70 to 140xc2x0 C., a vinyl-substituted aromatic compound content of from 0 to 35% by weight, a bromine number of from 0 to 30 g/100 g, a number average molecular weight of from 400 to 1,000, and a weight average molecular weight/number average molecular weight (Mw/Mn) ratio of 2.5 or less.
The fourth invention is to provide a process for producing the hydrogenated product of the copolymer of the third invention, which comprises conducting the copolymerization while adding a mixture of cyclopentadiene and/or dicyclopentadiene and a vinyl-substituted aromatic compound to a solvent in divided portions, and then conducting the hydrogenation to produce a hydrogenated product of a copolymer of cyclopentadiene and/or dicyclopentadiene and the vinyl-substituted aromatic compound, wherein the solvent is used in an amount of from 50 to 500 parts by weight per 100 parts by weight in total of cyclopentadiene and/or dicyclopentadiene and the vinyl-substituted aromatic compound. This fourth invention is provided by adding the hydrogenation step to the second invention.
The fifth invention is to provide a copolymer of cyclopentadiene and/or dicyclopentadiene and a vinyl-substituted aromatic compound, the copolymer having a softening point of from 60 to 130xc2x0 C., a vinyl-substituted aromatic compound content of from 30 to 90% by weight, a bromine number of from 30 to 90 g/100 g, a number average molecular weight of from 400 to 1,000, and a weight average molecular weight/number average molecular weight (Mw/Mn) ratio of less than 1.9.
The sixth invention is to provide a process for producing the copolymer of the fifth invention, which comprises conducting the copolymerization while adding a mixture of cyclopentadiene and/or dicyclopentadiene and a vinyl-substituted aromatic compound to a solvent in divided portions to produce a copolymer of cyclopentadiene and/or dicyclopentadiene and the vinyl-substituted aromatic compound, wherein a sulfur compound is caused to exist in the addition in divided portions.
The seventh invention is to provide a process for producing the copolymer of the fifth invention, which comprises conducting the copolymerization while adding a mixture of cyclopentadiene and/or dicyclopentadiene and a vinyl-substituted aromatic compound to a solvent in divided portions to produce a copolymer of cyclopentadiene and/or dicyclopentadiene and the vinyl-substituted aromatic compound, wherein at least one compound selected from the group consisting of a hydroxybenzene compound, a hydroxynaphthalene compound and a quinone compound is caused to exist in the addition in divided portions.
The eighth invention is to provide a hydrogenated product of a copolymer of cyclopentadiene and/or dicyclopentadiene and a vinyl-substituted compound which is obtained by hydrogenating the copolymer of the fifth invention, and which has a softening point of from 70 to 140xc2x0 C., a vinyl-substituted aromatic compound content of from 0 to 35% by weight, a bromine number of from 0 to 30 g/100 g, a number average molecular weight of from 400 to 1,000, and a weight average molecular weight/number average molecular weight (Mw/Mn) ratio of less than 1.9.
The ninth invention is to provide a process for producing the hydrogenated product of the copolymer in the eighth invention, which comprises conducting the copolymerization while adding a mixture of cyclopentadiene and/or dicyclopentadiene and a vinyl-substituted aromatic compound to a solvent in divided portions, and then conducting the hydrogenation to produce a hydrogenated product of a copolymer of cyclopentadiene and/or dicyclopentadiene and the vinyl-substituted aromatic compound, wherein a sulfur compound is caused to exist in the addition in divided portions. The ninth invention is provided by adding the hydrogenation step to the sixth invention.
Finally, the tenth invention is to provide a process for producing the hydrogenated product of the copolymer in the eighth invention, which comprises conducting the copolymerization while adding a mixture of cyclopentadiene and/or dicyclopentadiene and a vinyl-substituted aromatic compound to a solvent in divided portions, and then conducting the hydrogenation to produce a hydrogenated product of a copolymer of cyclopentadiene and/or dicyclopentadiene and the vinyl-substituted aromatic compound, wherein at least one compound selected from the group consisting of a hydroxybenzene compound, a hydroxynaphthalene compound and a quinone compound is caused to exist in the addition in divided portions. This tenth invention is provided by adding the hydrogenation step to the seventh invention.